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Dynamic DNS support for GPRS

By default most GSM providers assign dynamic IP addresses for their GPRS service, which means that each time the GPRS enabled device logs on to the GPRS network a different IP address is assigned to the device. Usually the option of having a fixed IP address for each GPRS device is only available for large account customers and not within reach for customers with a limited number of GPRS devices or for customers who want to set up a small pilot/evaluation project at first.

In the past the Necoso GPRS application solved this problem of 'dynamic IP addresses' by sending an SMS message containing the current IP address to the user each time the GPRS devices logs on to the GPRS network. This rather user unfriendly and unwanted for situations where there are many GPRS devices or the GPRS enabled devices are to be accessed by an automated process. (e.g. central server polling GPRS devices periodically) 

Necoso now has a solution for this problem. It is called 'dynamic DNS support' and is based on the free dynamic DNS service of the DNS provider. Necoso has developed an application for its GPRS products that enables automatic updating of a dynamic DNS account. Allowing a user or automated process to access the GPRS device using a static domain name (e.g. in stead of an ever varying IP address.


FAQ dynamic DNS support


Question: What does this dynamic DNS support for GPRS offer me?

Answer: To answer this question consider the situation with and without support for dynamic DNS:

Before, without dynamic DNS support:

Each time a GPRS enabled device logs on to the GPRS network it receives a different IP address. The Necoso GPRS software used a SMS message to report the new IP address to the user. The user has to read this SMS message on its mobile phone and enter the new IP address in its software (e.g. webbrowser) for getting access to the device.

Disadvantage is that it takes one SMS each time the GPRS device is assigned a new IP address. Additionally, it is user unfriendly and difficult to automate. (for those configurations where automated connections to GPRS devices are wanted, e.g. for periodic polling of GPRS devices by a central host computer)


Now, with dynamic DNS support:

The GPRS enabled device can be accessed using a domain name, e.g.:  This domain name is fixed, the IP address that belongs to this domain name is still changing with every GPRS session (hence the term ‘dynamic DNS') but the user is not bothered by this anymore. He/she now addresses the GPRS device using only its domain name. Knowledge of the actual IP address of the GPRS device is no longer required.


Question: How does this dynamic DNS support feature work at the GPRS device side?

Answer: After logging on to the GPRS network the GPRS device will automatically report its new IP address to a dynamic DNS account server (e.g. to update its dynamic DNS account. The GPRS network connection itself is used for this and it is a fully automated process. Once the account is updated, the DNS servers on the worldwide internet itself are updated within minutes, enabling access to the device with the same static domain name. No SMS is sent to the registered user to inform him of the new IP address, as this is no longer required.



1)    Saves money (no more SMS transmission with each GPRS log on)

2)    More user-friendly - No more SMS reading and typing of IP addresses.

3)    User interaction (SMS reading) no longer required, so ideal for automated logging/data retrieval using central internet     server.



1)   One time operation of opening a dynamic DNS account. With DynDNS  this is free and enables up to 5 domain names per account.

2)   After updating the dynamic DNS account on the DNS server it may take a short while before the DNS update is reflected to all DNS servers on the worldwide internet. According to DynDNS this may take up to 15 to 20 minutes. Our experience is that usually this takes less than 2 minutes. For most M2M GPRS application this is acceptable.


Question: What do I have to do for enabling this dynamic DNS support for my GPRS devices?

Answer:  You have to open a dynamic DNS account with DynDNS. Refer to their website at for more information. Next, the account information for your account must configured into with the Necoso DynDNS application. That's all.


Question: I have an existing GPRS product from Necoso - can I use dynamic DNS too?

Answer:  Yes, but you will need to update your product to the latest Necoso software - contact us for more information.


Question: Does this dynamic DNS feature work with all SIM cards available from Dutch GSM providers?

Answer: No, only with SIM cards that are assigned a public IP address when they log on to a GPRS network. A public IP address is an IP address which is unique within the range of IP addresses valid for the worldwide internet and can therefore be addressed directly from any workstation or computer on that same worldwide internet.

Currently (as per February 2004) only SIM cards from Dutch GSM providers KPN, Orange en T-Mobile are assigned public IP addresses. SIM cards from the other Dutch GSM providers are assigned non-public IP addresses, i.e. addresses that are 'hidden' behind a NAT server and can therefore not be accessed directly from the worldwide internet. (although access from the GPRS device to the device to the world wide internet is still possible - the direction of connection initiative is important here!)


Question: Does this dynamic DNS feature work also for the Necoso GPRS-to-Ethernet and GPRS-to-Serial bridges?

Answer: Yes, Necoso has adapted the G2E and G2S applications for cooperation with the new dynamic DNS application.


Question: Does this dynamic DNS feature work also work when I enable the ‘Smart-On’ option?

Answer: Yes.


Question: For what kind of GPRS applications should I consider using this dynamic DNS feature?

Answer: First of all dynamic DNS support was intended for the kind of GPRS applications where interactive access to a device is wanted, for example with a webbrowser. The initiative for setting up a connection here is at the user/client side, not at the GPRS device side. The dynamic DNS support saves you the IP address hassle as well as the costs for the SMS messages that must otherwise be transmitted by the device.

Next, dynamic DNS support is intended also for those non-interactive applications where an automated process is to be implemented that periodically contacts all GPRS devices in the field, e.q. for data retrieval or passing on the latest set points.

With dynamic DNS these devices can now be addressed using their individual domain names. The central server no longer needs to receive and interpret the SMS message that are sent by the devices when they log on to the GPRS network. In other words, this saves a lot of (hardware and software) hassle at the side of the central server.


Question: What if the DNS account update process over GPRS fails?

Answer: If this process for some reason fails, then first the GPRS device will perform a number of retries. If all of these retries fail, then the GPRS device will assume human intervention is required and will send a single notification SMS message to a pre-configured service number. Of course, access to the GPRS device at this point is still possible using its IP address. Which - as before- can be retrieved always by sending a command SMS to the GPRS device.


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Phone: +31 (0)55-3601410, fax +31 (0)84-7246122
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Last updated:07-jan-2013